The present invention relates to a system for treating an elongated workpiece. More particularly this invention concerns a method of and apparatus for bending a metallic bar or rod.
My above-described earlier application discloses a multi-function metal-working machine having a support with spaced ends and a longitudinal passage extending intermediate these ends. A carriage is mounted for displacement in and lengthwise of the passage and means is provided for so moving the carriage. At least one first tool holder is provided on the carriage and mounting means is located at least on one end of the support for mounting at least one second tool holder. The carriage is moved by means of a hydraulic or mechanical drive. A plurality of tool holders are mountable on the mounting means detachably and at least some of these tool holders are provided with projecting stub shafts.
It is known in such machines to form rods or bars, usually of steel, into rings or helicoids. This is carried out as described in my earlier patent application by passing the elongated metal workpiece between three rollers that define an arcuate path. The two end rollers engage the convex outside of the workpiece and the middle roller engages between these end rollers against the concave inner side of the workpiece. The rollers all rotate about parallel axes and at least the axis of the middle roller is displaceable toward the plane defined by the axes of the end rollers. Typically in such an arrangement the middle roller is moved inwardly after each pass of the workpiece between the rollers so as to bend the workpiece with each pass to an increasingly smaller radius of curvature.
Such an arrangement works with very little difficulty so long as the bending radius is not too small and/or the workpiece is not too thick. When, however, a relatively small bending radius is required, a relatively large-diameter workpiece must be bent, or a workpiece must be bent edgewise, it is necessary to form grooves on the bending rollers in order to guide the workpiece as it is bent. Otherwise the workpiece will slip on the tools and uniform bending results will not be obtained.
The principal problem created by the provision of such guide grooves is that when a thick workpiece must be bent, a workpiece must be bent edgewise, or a workpiece must be bent through a relatively small radius, ridges form on the concave inner surface of the workpiece as well as on the sides of the workpiece flanking this inner concave side. Such formations increase the size of the workpiece so as often to cause it to jam up in the guide groove and prevent the machine from operating altogether. Thus it is necessary to provide relatively wide guide grooves in such devices in order to prevent such jamming, with the concomitant disadvantages that uneven bending results are often obtained.